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UBC Theses and Dissertations

Spatially resolved laser induced fluorescence studies in the three electrode direct current plasma Le Blanc, Charles Wilfred


Spectrcchemical emission from analytes in the three electrode direct current plasma has been found to be sensitive to the presence of easily ionizable elements (EIEs) as concomitants in sample matrices. An understanding of the mechanisms by which these EBEs affect analyte emissions is complicated by the fact that both emission enhancements and suppressions of ion and atom lines have been observed. In order to gain further insight into this effect, a fluorescence spectrometer was built and used as a spatial and spectral probe to obtain analyte population distribution profiles in the plasma. The spatial distribution of the analyte in the plasma was found to be quite complex. Most of the analyte skirted around the plasma core and did not enter the analytical emission zone. The area in the plasma where emission was observed was relatively small compared to the spatial population distribution of the analyte which suggests that the amount of analyte contributing to the emission was a small fraction of the total analyte population present. Three dimensional fluorescence profiles of Ba⁺concentrations in the plasma were determined with and without sodium present as the EIE. The presence of the EIE in the sample did not alter the spatial distribution of the Ba⁺ population significantly but did appear to cause an ionization suppression. Emission profiles of the Ba(I) 553.548 nm and Ba(H) 493.409 nm lines were also obtained with and without an EIE present in the sample matrix. In both cases, the presence of the EIE caused emission enhancements; however, the effect was greater for the Ba(I) line than for the Ba(II) line which supports with the proposed ionization suppression mechanism.

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